Early Fermi LAT observations of the Vela pulsar

Early Fermi LAT observations of the Vela pulsar Massimiliano Razzano on behalf of the Fermi LAT Collaboration INFN-Pisa massimiliano.razzano@pi.infn.it M.Razzano - 44th Rencontres de Moriond

ID of Vela pulsar • Radio pulsation discovered in 1968 in the Vela SNR, bright pulsar: S1.4Ghz~1.5 Jy • Located RA=08:35:20.61,dec=-45:10:34.87 (near the Galactic plane @b~-2.8˚) • D~287+19-17 pc (VLBI parallax in 2003)‏ • P:~89 ms; Pdot ~3x10-13 s/s • Young pulsar tc~11 kyr • Energetic Edot~7x1036 erg/s • Bsurf ~3.4x1012 G 7 high confidence gamma-ray pulsars Low confidence gamma-ray pulsars (D. Thompson, 2003)‏

A huge gamma-ray telescope ! Kanbach et al. 1980 Kanbach et al. 1994 Thompson et al. 1975 Pellizzoni et al. 2008 Abdo et. al 2008

A huge teamwork ! • Large collaborative effort of scientific/instrumental analysis! • See Abdo et al. 2009 ApJ in press,arXiv:0812.2960

Point Spread Function Excellent agreement with pre-launch expectations below few GeV Stefano Germani’s talk about on-orbit performance verifications & monitoring Flight data on Vela used for testing the pre-launch expectations The PSF is very sharp at high energy

First Fermi Vela light curve 100 MeV < E < 10 GeV ~50000 photons ! Remarkably sharp peaks; features to ~0.3 ms Turns almost completely off between the double pulses

Light curve evolution with energy Large LAT energy window puts Vela pulsar in multiwavelength context !

Vela in Radio Coherent radio emission Parkes 64m telescope RMS residuals 90s log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

Synchrotron optical/uv HST STIS/MAMA 4.1-6.5 eV (Romani et al., ApJ 2005) Vela in UV log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

Thermal soft X-rays XMM PN Soft X-rays log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

Synchrotron hard X-rays RXTE PCA (Harding et al., ApJ 2002) Hard X-rays log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

Vela in g-rays • Curvature g-rays • Fermi LAT • Energy dependent pulses • First peak softer than second • Known from EGRET log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

Vela in g-rays • Curvature g-rays • Fermi LAT • Energy dependent pulses • First peak softer than second • Known from EGRET • 3rd Peak, which shift in energy • New result ! log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

Vela in g-rays • Curvature g-rays • Fermi LAT • Energy dependent pulses • First peak softer than second • Known from EGRET • Trailing peak survives (known from EGRET) log nFn (Jy Hz) log E2 dN/dE (erg cm-2 s-1)

Phase-averaged spectrum Consistent with b=1 (simple exponential) b=2 (super-exponential) rejected at 16.5s No evidence for magnetic pair attenuation: Near-surface emission ruled out

The Vela pulsar movie • E<300MeV (red) • 300MeV<E<1GeV(Green) • E>1GeV (blue)

Summary of key results Vela pulsar Phase-averaged spectrum Simple exponential cutoff Ec = 2.9 ± 0.1 GeV Inconsistent with magnetic pair attenuation, thus favoring outer magnetosphere emission models Energy-dependent pulse profile First peak is softer than second peak (confirming EGRET) Sharpest features to ~0.3 ms. Peak in bridge region (phase ~ 0.3) shifts to later phase with increasing g-ray energy Upper limit on unpulsed emission (>100 MeV) 1.8x10-7 ph/cm2/s 95% C.L. upper limit on unpulsed emission, e.g. PWN (Talk of Marie-Helene Grondin) Stringent limits or measurement will be available with more livetime See Abdo et al. 2009 ApJ in press, arXiv:0812.2960 Contact authors R. Romani and M. Razzano Fermi LAT & Vela Working as designed, performance as expected e.g. Vela results demonstrate timing and angular resolution below few GeV (Talk of Stefano Germani)

Early Fermi LAT observations of the Vela pulsar

Early Fermi LAT observations of the Vela pulsar

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